Cathodic pseudopolarography: A new tool for the identification and quantification of cysteine, cystine and other low molecular weight thiols in seawater

Novel insights into the molecular structure of non-volatile marine dissolved organic sulfur

“…4). There are traces of thiols in seawater (Al-Farawati and van den Berg, 2001;Dupont et al, 2006;Laglera et al, 2014), but our results indicate that they are not a major fraction of DOS that is recovered via SPE from marine waters. …”

Chemical Speciation of Copper in a Salt Marsh Estuary and Bioavailability to Thaumarchaeota

“…For example, thiols can be microbially transformed from one type to another: glutathione can be transformed into mercaptoacetate and mercaptoethanol via cysteine and 3-mercaptopyruvate (Kiene et al, 1990). Although, voltammetry can distinguish between some similar thiols (such as glutathione and cysteine) it lacks resolution to conclusively distinguish between other similar compounds (e.g., thiourea and thioacetamide) unless the deposition potential is varied in detail (Laglera et al, 2014). The natural thiols detected here could therefore be a mixture of thiols with similar peaks varying seasonally, and/or include degradation products of localized algal blooms, and include different sulfur species.…”

Electrochemical Evidence of non-Volatile Reduced Sulfur Species in Water-Soluble Fraction of Fine Marine Aerosols

“…In different aquatic ecosystems, electrochemical methods have been widely used for the characterization and determination of different sulfur (S) species, comprising dissolved and/or particulate inorganic and organic S compounds, including thiols ( [1][2][3][4][5][6][7][8][9][10][11][12] and references therein). Strong interaction between mercury electrode (Hg) and S species is a background for their electroanalytical determination and speciation at the Hg electrode.…”

“…Strong interaction between mercury electrode (Hg) and S species is a background for their electroanalytical determination and speciation at the Hg electrode. The methodology is based on the tendency of inorganic and organic reduced S species (RSS) to deposit a HgS layer [1][2][3][4][5][13][14][15] and/or RS-Hg complexes [9,10,15] (term "complex" refers to a different type of interaction between the analyte and the Hg electrode) during an accumulation step at the deposition potential (E d ) around −0.2 V vs. the reference electrode (Ag/AgCl). In solutions containing sulfide anions, an insoluble HgS layer is formed during the deposition step at the Hg surface by the reversible process of a two-electron-transfer oxidation of Hg at potentials more positive than −0.5 V vs. the reference electrode (Ag/AgCl) (Equation (1)) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]:…”

“…The same process occurs during the interaction of Hg with some other organic (thiourea, thiols, oxines, thioanions) and inorganic S species (polysulfides, dissolved and colloidal S, labile chalcogenides, i.e., CuS, PbS, HgS, FeS, Ag 2 S). During the potential scan toward negative values, layers of HgS and adsorbable RS-Hg complexes (in the case of DMS, DMDS, cysteine, glutathione) are reduced between −0.45 and −0.70 V (vs. Ag/AgCl) with facilitated reduction of the RS-Hg complexes at a more positive potential than −0.68 V (vs. Ag/AgCl) where HgS reduction occurs [2,9,10,15,16].…”